For the purpose of promoting traffic safety and preventing traffic accidents, the Intelligent Transport System (ITS) has now been proposed. According to the ITS, a communication device is installed on the roads. Information sent out through the antenna of the communication device is received at an in-vehicle device mounted on a running vehicle. Usage of such information by the in-vehicle device allows the safety in association with the drive of the vehicle to be improved (refer to Japanese Patent No. 2806801).
For a road-vehicle wireless communication, an arm is extended towards the roadway from a pole installed on the sideway or the like, and an antenna of the communication device is attached on the arm from the standpoint of ensuring the line of sight in wireless communication. In the case where the line of sight can be ensured in the absence of an arm, the antenna is attached directly to the aforementioned pole.
For the purpose of installing the antenna of the communication device at the road, it is not economical to newly install a pole just for the antenna. It is also not preferable from the standpoint of the aesthetic view of the street.
Since vehicle sensors, heads of optical beacon and the like are installed along the road, it may be possible to install the antenna at the poles and arms to which the sensors and heads are attached. However, this is not preferable from the standpoint of aesthetic purpose.